This won't be exhaustive and we've still got a long way to go on our project, so if you have anything to add please let me know!
1. Plan in advanceGood tradies are often booked up well in advance. We had to accept our second choice plasterer in June because our first choice was (in his words) booked for the rest of the year. That's an extreme example, but especially for the key folk (builders!) it does pay to get in before you need the work done.
2. Ask for recommendationsIf you have friends who've had work done recently, ask them what they thought of their tradies, and if the feedback is positive, pinch their contact details.
Ask around at work, on social media, anywhere really. The catch is you need to trust the person giving the referral - sometimes people recommend folk because they know and like them, which is not the same as having had work done by them. We had a builder recommended this way for a small job at our previous house, and it didn't end well for us - we had to repaint a wall that shouldn't have needed touching, as well as remedying some of the shoddy building work ourselves.
If you're struggling for recommendations you could try popping your job up on Builders Crack, which does have reviews - but I reckon the good ones (as a gross generalisation) don't bother with sites like that because they do well enough out of recommendations, and so the standards are a bit lower. We've used it a couple of times, and though it worked out okay for the one job we completed through it, we won't use the tradie again. The other jobs I listed didn't yield satisfactory responses so we looked elsewhere. Not fully inspiring. That said, if it's something small and simple it could work well.
3. Check reviewsA quick Google is a good place to start. If they have listings on any sites which do ratings check the comments and scores of other customers; if they have their own websites hopefully they'll have some testimonials there (though obviously these will be cherry-picked). Mainly I figure anything really bad (like a Fair Go appearance) would probably show up in an online search - unlikely but worth checking for.
4. Get multiple quotesQuotes are not just about the money. The quoting process also gives you a chance to talk to the tradie and get a feel for how they operate, and most importantly, how easy they are to communicate with. Which leads me to...
5. Ask questions
Ask as many questions as you have. If the person you're dealing with is uncomfortable answering them you don't want to be paying them to work in your home. In most jobs things will crop up during the process that need addressing - if there's not easy, clear communication things can get complicated very quickly.
It's probably obvious, but once you have the quote make sure you're explicitly clear on what's included.
So tell me - do you have any tips you'd add? Have you had any particularly stellar - or utterly terrible - experiences with tradies?